Aflatoxins and ochratoxin A in tea prepared from naturally contaminated powdered ginger.

The migration of several major mycotoxins, aflatoxins B(1) (AFB(1)), B(2), G(1), and G(2) (AFT, total of the aflatoxins) and ochratoxin A (OTA), from naturally contaminated powdered ginger to surrounding liquid (tea) was investigated. The toxins are commonly found in cereal grains and are toxic, carcinogenic and thermostable. Ginger root is widely used for digestive problems. Powdered ginger (2 g) found to contain AFT and OTA was placed in an empty heat sealable tea bag. The tea bag was heat-sealed and used to prepare tea under different conditions: temperature (50 and 100 degrees C), time (5 and 10 min) and volume (100 and 200 ml). The tea bag was placed in hot water and stirred every 1 min for 5 s during the first 5 min of steeping. After steeping, the tea bag was removed and the tea and ginger residue (in the tea bag) were analysed separately for AFT and OTA. After extraction and immunoaffinity column (IAC) clean-up, the isolated AFT and OTA were separated by reversed-phase liquid chromatography and quantified using a fluorescence detector. At 100 degrees C, approximately 30-40% of AFB(1) and AFT and 20-30% of OTA in the contaminated ginger were found in the ginger tea; the total amounts of AFT and OTA in tea varied less than 5% under the three conditions of preparation. At 50 degrees C, about 10% of OTA and AFT were found in tea. This is the first study on the migration of AFT from botanicals to tea. It is also the first to study the distribution of AFT and OTA from powdered ginger to tea and ginger residue.

Effect of processing on ochratoxin A content in dried beans.

Dried pink beans naturally contaminated with ochratoxin A (OTA) and dried carioca beans artificially contaminated with OTA by inoculation with Aspergillus ochraceus (ATCC 22947) were tested for ochratoxin A levels as follows: dried beans were washed with water for 2, 60 or 120 min, soaked in water for 60, 120 min or 10 h, and cooked for 60 or 120 min. At each step, test water and beans were separated. Test water, raw beans and cooked beans were analyzed for OTA. The amount of OTA partitioned into water and in residual beans was determined by methanol-sodium bicarbonate extraction, buffer dilution, immunoaffinity column cleanup, liquid chromatographic separation and fluorescence detection. The results demonstrated that the distribution of OTA in processing water and beans depends on the method of preparation. All treatments (washing, soaking and cooking) when applied individually reduced the amounts of OTA retained in bean flour and whole beans. Higher amounts of OTA remained in whole beans than in bean flour after removing the processing water. The combination of the three treatments eliminated about 50% of the toxin from whole beans. This study provides evidence that discarding the washing, soaking and cooking water leads to a significant reduction in OTA contamination in dried beans.

Adsorption of di-2-pyridyl ketone salicyloylhydrazone on Amberlite XAD-2 and XAD-7 resins: characteristics and isotherms.

The adsorption of DPKSH onto Amberlite XAD-2 (styrene resin) and XAD-7 (acrylic ester resin) has been investigated, at (25+/-1) degrees C and pH 4.7. The experimental equilibrium data were fitted to the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) models. These three models provide a very good fit for both resins and the respective constants KL, KF, and KDR were calculated. For the same DPKSH concentration interval, the minimum time of contact for adsorption maximum at XAD-7 was smaller than at XAD-2 and the maximum amount of DPKSH adsorbed per gram of XAD-2 is smaller than at XAD-7. The investigation indicates that the mean sorption energy (E) characterizes a physical adsorption and the surfaces of both resins are energetically heterogeneous. The constants obtained in these studied systems were correlated and compared with those obtained for the silica gel/DPKSH system.

Kinetic modeling of adsorption of di-2-pyridylketone salicyloylhydrazone on silica gel.

The kinetics of DPKSH (di-2-pyridylketone salicyloylhydrazone) adsorption onto silica gel has been investigated at (25+/-1) degrees C and pH 1 and 4.7. The kinetics of adsorption of DPKSH is discussed using three kinetic models, the first-order Lagergren model, the pseudo-second-order model, and the intraparticle diffusion model. The adsorption of DPKSH, at pH 1 and 4.7, onto silica gel proceeds according to the pseudo-second-order model and the correlation coefficients were very close to 1. The intraparticle diffusion of DPKSH molecules within the silica gel particles was identified as the rate-limiting step. The parameters of the pseudo-second-order model are q(max,calc)=1.02 x 10(-4) and 1.5 x 10(-4) g DPKSH/g silica; k(2)=3.01 x 10(4) and 9.67 x 10(4) h(-1)g silica/g DPKSH, respectively, for pH 1 and 4.7.

Adsorption of di-2-pyridyl ketone salicyloylhydrazone on silica gel: characteristics and isotherms.

The adsorption of DPKSH onto silica gel was investigated, at 25+/-1 degrees C and pH 1, 4.7 and 12. For the same DPKSH concentration interval, the minimum required time of contact for adsorption maximum at pH 4.7 was smaller than at pH 1 and the maximum amount of DPKSH adsorbed per gram of silica at pH 1 is smaller than at pH 4.7. At pH 12 the DPKSH adsorption onto silica gel was not significant. The adsorption data followed Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The maximum amount of solute adsorbed (m(ads)(max)) and the adsorption constant, K(L), were derived from Langmuir isotherm. The Freundlich constants 1/n and K(F) related, respectively, to the energetic heterogeneity of adsorption sites and an empirical constant were evaluated. The mean sorption free energy (E) of DPKSH adsorption onto silica gel was calculated from D-R isotherm indicating a physical adsorption mode. Finally, conductimetric titrations showed the silica particle basicity and acidity as 0.002 and 0.3mmolg(-1), respectively.

Occurrence of aflatoxins M(1) and M(2) in milk commercialized in Ribeirão Preto-SP, Brazil.

Aflatoxins are toxic metabolites found in foods and feeds. When ruminants eat foodstuffs containing aflatoxins B(1) and B(2), these toxins are metabolized and excreted as aflatoxin M(1) and M(2) in milk. The aim was to determine the incidence of these aflatoxins in commercial milk collected from supermarkets in Ribeirão Preto-SP, Brazil, and consisting of 60 ultrahigh temperature (UHT) milk samples and 79 pasteurized milk samples. The milk samples were analysed according to method 986.16 of AOAC International. None of the milk samples analysed were contaminated with aflatoxin M(2), and aflatoxin M(1) was detected in 29 (20.9%) of samples in the range 50-240 ng l(-1). The results show that despite a high occurrence of aflatoxin M(1) in commercial pasteurized and UHT milk sold in Ribeirão Preto in 1999 and 2000, the contamination level of these toxins could not be considered a serious public health problem according to MERCOSUR Technical Regulations. However, levels in 20.9% of the milk samples exceeded the concentration of 50 ng l(-1) permitted by the European Union. Although it is not necessary to continue monitoring the incidence and levels of aflatoxins M(1) and M(2) in milk samples, surveillance could be appropriate.

Study of complex formation in the manganese(II)/azide system.

The complex formation between Mn(II) cations and N(3)(-) anions was studied in aqueous medium at 25 degrees C and ionic strength 2.0 M (NaClO(4)). Data of average ligand number, n (Bjerrum's function), were obtained from pH measurements on the Mn(II)/N(3)(-)/HN(3) system followed by integration to obtain Leden's function, F(0)(L). Graphical treatment of data and a matrix solution of simultaneous equations have given the following overall formation constants of mononuclear stepwise complexes: beta(1)=4.15+/-0.02 M(-1), beta(2)=6.61+/-0.04 M(-2), beta(3)=3.33+/-0.02 M(-3), beta(4)=0.63+/-0.01 M(-4). A linear plot of log K(n) vs. (n-1) shows no change in the configuration during complex formation. Slow spontaneous oxidation of solutions to Mn(III) occurs when the N(3)(-) concentration is greater than 1.0 M.